Superheterodyne converter



Feb. 18, 1947. A. H. TURNER 2,415,977

I SUPERHETERODYNE CON-ERTER Filed Marchy s, 1943 2 sheets-sheet 1 Feb. 18, 1947. A, H TURNER 2,415,977

SUPERHETERODYNE CONVERTER Filed March 8, 1943 2 Sheets-Sheet 2 Srmentor Patented Feb. l, i947 SUPERHETERODYNE CONVERTER Delaware Application March 8, 1943, Serial No. 478,453 s claims. (ci. 25o- 2.0)

to radio receivers for receiving high frequency signals such as centimeter My invention relates wave signals. It relates particularly to a radiofrequency amplifier, local oscillator and GGSCOT unit for converting the incoming radio-frequency signals to intermediate-frequency signals.

The usual method of coupling the radio-frequency amplifier and the local oscillator to the detector or converter tube has been by using untuned coaxial lines. This has the disadvantage that radio-frequency signal energy is lost in both of these coaxial lines, and oscillator energy is also lost in both of thelines since both lines are coupled tc the converter tube.

An object of the present invention is to provide a frequency converter unit in which the energy loss is a minimum. A further object of the invention is to provide an improved superheterodyne converter unit for the reception of ultra high frequencies.

In a preferred embodiment of the invention the radio-frequency ampliiier and the local scillator are of the type having concentric line plate circuits. These concentric line circuits are positioned parallel to each other and the detector or converter tube is iocated between them and inside a box-like compartment of conducting material which bridges the two parallel lines. Windows or openings are provided in the outer conductors of the two plate circuits; these windows form openings in the bridging compartment. Potential diierences appear across the conductor openings to circulate radio-frequency and oscillator currents which excite the grid circuit of the detector tube.

The invention will be better understood from the following description taken in connection with the accompanying drawings in which Figure 1 is a view of one embodiment of the invention, the view being partly in section taken on the line I-I of Fig. 2,

VFigure la is a view that is referred to in eX- plaining the operation of the invention,

Figure 2 is a View taken on the line 2 2 of Fig. 1,

Figure 3 is a View taken on the line 3--3 of FiaZ. v

Figure 4 is a view taken on the line '4 4 of Fig. 3, and

Figure 5 is a circuit diagram showing the equivaient circuit diagram for the unit illustrated in Figs. 1 to 4.

In the several figures similar parts are indicated by similar reference characters.

Referring to the drawings, particularly to Figs.

1 and 2, the radio-frequency amplifier tube I Il, the oscillator tube II and the detector tube I2 are triodes of the light-house type, RCA 446A or General Electric type ZP 464, for example, although it should be understood that the invention is not limited to this specific type of tube. The grid and plate terminals of the tube I are the rings I3 and It, respectively, which are supported by glass sections of the tube. Corresponding terminals for the tubes II and I2 are shown at I5, I1 and I-B, I9, respectively. The cathode terminals for the tubes II), II and I2 are shown at 2|, 22 and 23, respectively. The heater terminals for the cathodes of tubes I0, H and I2 are shown at 26, 2l, at 28, 29 and at SI, 32, respectively. The various electrode terminals are also indicated in the equivalent circuit diagram of Fig. 5.

The R.F. amplier tube It has a tuned gridcathode circuit comprising an inner conductor 33 and an outer conductor 34 which form a concentric line. The connection from the cathode of tube I0 to the end of the inner conductor 33 for the high frequency signal is through internal tube capacity between the cathode and the outer metal shell 36 and through the metal fingers 3l to conductor 33. This internal capacity is indicated at CI in Fig. 5. The connection from the grid of tube Iii to the end of the outer conductor Si is from the grid terminal I3 to metal fingers 38 which are conductively connected to the end of conductor'34.

'Ihe grid-cathode line 33-315 is tuned by means of a slidable shorting ring 39. In Fig 5 the line 33-34 is represented by the lumped inductance 33-3i, Biasng is provided by means of a cathode resistor tl. The received R.`F. signal is applied to the R.F. amplifier through a concentric line 42 which has its inner conductor capacitively coupled to the tube shell 36 by means of a small capacitor plate 43.

The tuned plate circuit is a concentric line comprising an inner conductor 46 having one end connected to the plate terminal It and an outer conductor 41 having one end connected to the grid terminal I 3 through the ngers 32. The line dii-lll is tuned by means of a plug 48 which may be moved longitudinally by rotating a threaded insulating rod 49 to change the capacity C2 at one end oi" the line. Operating voltage is applied to the lplate terminal I4 through an R.F. choke coilEI. In- Fig. 5 the tuned line l5-tl isrepresented by the lumped inductor @6L-4l.

.A narrow window or opening 52 in one side of the outer conductor 41 is provided for coupling into the detector tube I 2 as explained hereinafter.

The oscillator tube ll preferably is connected to operate as an oscillator of the grounded grid type as described and claimed in my copending application Serial No. 428,665, filed January 29, 1949.. and entitled Oscillator.

The oscillator has a tuned cathode-grid circuit comprising an inner conductor 53 and a concentric outer conductor 54 which form a concentric' line. This line is tuned by means of a shortng ring S. The connection from the inner conductor 53 to the cathode of tube I I 4is through the fingers 5l and through internal tube capacity, the

latter being indicated at C4 in Fig. 5. The tuned line 53--55 is represented by the lumped inductoi" 532-54 in Fig. 5. A suitable cathode bias resistor 55 is connected between cathode terminal 22 and ground.

In this oscillator design,- the connection bctween the grounded outer conductor 54 and the grid terminal IS, instead of being adirect current connection, is through' a capacitor connecnon which is fenced by providing a mica ring or washer 53 that spaces the finger supporting ring 59 from the turned-in portion 54a of the outer conductor 54,. this capacitor being indicated at C5 in Fig. 5. The primal-Ky purpose' Of this capacitor is to provide the plate-'to-athode c'o'upling for oscillator feedeback. A grid-leali` iesistor is shown at 6B. u

The tuned anode-grid circuit comprises an inner conductor 5I and an outer conductor 62 which form a concentric line that is tuned by a capacity changing plug G3, just as described in connection with the R.-F. arnrililier.0 The capacity that is changed by plug 63 is indicated at C6. The tuned line Iii- 52 is indicated in Fig. 5 as a lumped inductor 5I'6`2. The coupling from the oscillator' to the detector is through a window o'r opening 65 in the outer conductor 62 as will be explained below.v A cover or casing 61 may be provided for the R.-F. amplier, the oscillator and the detector portions of the unit. Referring now to the detector or converter tube I2' and. te the method of' coupling inte it, aboalike compartment 68 of conducting material bridges the outer conductors 4'! and 62 of the R.F. amplier and oscillator plate circuits, respectively. The detector tube l2 is set into the compartment B8 in inverted position in this particular example as shown more clearly in Figs. 2 and 3, the view in Fig'r 3 being taken at right angles to the one in Fig. 2.

The compartment G8 comprises end portions m and n and top and bottom portions o and 37, respectively. 'I'he sides of the compartment 68 are formed by the surface portions of the plate circuit conductors 4l and 62 containing the narrow vertical slit-like opening 52 and the horizontal rectangular opening 66, respectively.-4

The connections to the three electrodes of the tube I2 are made as follows: The thimble portion 49a of the anode terminal ts into a clip 'II which is supported by an insulating sheet 'l2 of mica or the like. Anode voltage is supplied to the clip 'II and to the anode terminal Illa through a conductor 73.- As shown in Figs. 3 and 5, the anode circuit includes an intermediate frequency transformer le. The cathode biasing connection is through a bias resistor T6 (Figs. 2 and 5) The cathode connection for the R.-'F. signal and the oscillator signal is from the top portion o of the compartment 68, through flexible ng'ers 'i8 (Fig. 3) to the metal shell of the tube I2, and

through internal tube capacity (represented by capacitor C1 in Fig. 5) to the cathode of tube I2. The grid connection is through a metal tab 8l set in one corner of the compartment 68 and having iiexible lingers 82 in contact with grid terminal I8.

The coupling into the grid-cathode circuit of detector tube I2 for the R.-F. signal is obtained with the above-described connections because of circulating currents induced by the presence of the window or opening 52 which causes the current to low around the opening as indicated by the broken lines in Fig. 1a. Thus the R.F. current has' a transverse component represented by the arrow y which produces a potential drop between the cathode and grid connecting tabs I8 and 8,2, respectively. Also, there is a circulating current which ilows through the tab 8! to the grid of tube I2 and through the internal gridcathode capacity to the cathode of the upper side of conductor lil, thus producing a corresponding voltage drop along the tab 8|. At these ultra high frequencies the paths traversed by the currents present inductive reactances. Therefore, the coupling from the tuned anode circuit 13E-lil into the detector tube I2 may be represented as in Fig. 5 where the portion of conductor 4l along the opening 52 and common to the R.F. ampliner and detector circuits is represented by an inductor SI which is inductively coupled to the R.-F. amplier plate circuit.

An adjustable arm 83 of springy material may be connected to the outer plate conductor il on one side of the opening 52 and positioned in capacitive relation to the grid terminal ring i3 at a point diametrically opposite the tab 8l. The capacity between the arm 83 and the terminal ring IB, which is represented in Fig. 5 by capacitor C8, may be adjusted by means of a rotatable threaded rod Se (Fig. 3) which moves a flat spring 85 and a pin 8l of insulating material in or out. The pin B'l engages the spring arm 83 to make it move in or out with the pin 8'! and thus vary the value of capacity C8 for tuning the input circuit of the tube l2. In some designs it may be found that the arm 83 can just as well be omitted.

The coupling of the oscillator to the gridcathode circuit of the detector tube may be due to the fact that the opening 66 is large enough to permit leakage of suicient electromagnetic and electrostatic iield from the tuned line iii- 52 for producing sufficient coupling. It will be noted, for example, that if electromagnetic lines of force cut the tab 8|, a potential diierence between the grid and the cathode of tube I2 will be induced. Judging from the operation of the apparatus, however, the coupling appears to be conductive, that is, it appears to be the same kind of coupling as that between the R.F. amplifier and the detector tube.

It has been found desirable to provide a series resonant circuit 88', 89 (Fig. 5) across the plate circuit of the tube I2, the resonant circuit being tuned to the R.F. signal frequency. This increases the conversion efciency and provides considerable tuning of the converter grid circuit through anode reaction. The mechanical construction for the series-resonant circuit 8889' is' best shown in Fig. 3 where an adjustable plate portion S8 is spaced from the clip "Il by the mica sheet 'l2 to provide the capacity 88'.v The plate portion 88 is adjustably supported by a spring arm Se which constitutes the inductor 89'. The capacity 88 may be adjusted by means of a rotatable screw-threaded rod 9 l, the end of which acts as a stop for a lug 92 fastened to the plate portion dil.

From the foregoing description it will be apparent that I have avoided the use of coupling lines and have avoided the losses associated therewith. Among the essential features of the invention are the compartment which bridges the tuned anode circuits and which has the converter tube set therein, and the openings in the tuned anode conductors for providing the desired coupling. It should be understood that the invention is not to be limited to the theory of operation that has been given, although applicant believes that his explanation of the way in which the coupling circuits function is substantially correct.

I claim as my invention:

i. A signal mixing unit comprising two Vacuum tubes each having an output circuit comprising a tuned concentric line, said tuned lines being positioned with a conductor ci one line adjacent to a conductor of the other line, a compartment of conducting material bridging said adjacent conductors, a mixer tube having at least one electrode terminal positioned inside said compartment and electrically connected thereto, each of said adjacent conductors having an opening therein looking into said compartment whereby said output circuits are coupled to said mixer tube, an output circuit for said mixer tube.

2. A signal mixing unit comprising a vacuum tube having a tuned output circuit which consists oi a concentric line having an inner conductor and an outer conductor, a second vacuum tube having a tuned output circuit which consists of a concentric line having an inner conductor and an outer conductor, a compartment of conducting material bridging `said outer conductors, a mixer tube having at least one electrode terminal plositioned inside said compartment and electrically connected thereto, each of said outer conductors having openings therein looking into said compartment whereby said output circuits are coupled to said mixer tube, and an output circuit for said mixer tube.

3. A frequency converter unit comprising a radio-frequency amplier having a tuned plate circuit which consists of a concentric line having an inner conductor and an cuter conductor, an oscillator having a tuned output circuit which consists of a concentric line having an inner conductor and an outer conductor, a compartment of conducting material bridging said outer conductors, a detector tubn having at least one electrode terminal positioned inside said compartment and electrically connected thereto, each of said outer conductors having openings therein looking into said compartment whereby said arnplier and said oscillator are coupled to said detector, and an output circuit for said detector.

4. A frequency converted unit comprising a radio-frequency amplifier having a tuned plate circuit which consists of a concentric line having an inner conductor and an outer conductor, an oscillator having a tuned output circuit which consists of a concentric line having an inner conductor and an outer conductor, said concentriclines being substantially parallel to each other, a. compartment of conducting material bridging said outer conductors, a detector tube having at least one electrode terminal positioned inside said compartment and electrically connected thereto, said detector tube being positioned with its longitudinal aXis at right angles to the longitudinal axis of said concentric lines, each of said outer conductors having openings therein looking into said compartment whereby said amplifier and said oscillator are coupled to -said detector, and an output circuit for said detector.

5. A frequency converter unit comprising a radio-frequency amplifier having a tuned plate circuit which consists of a concentric line having an inner conductor and an outer conductor, an oscillator having a tuned output circuit which consists of a concentric line having an inner conductor and an outer conductor, a compartment of conducting material bridging said outer conductors, a detector tube having an input circuit including input electrodes and having at least one input electrode terminal positioned in- Vside said compartment, each of said outer conductors having openings therein looking into said compartment to couple said amplifier and said oscillator to said detector, a portion of one or said outer conductors adjacent to the opening therein being common to said detector input circuit and to the tuned circuit in which said last conductor is included, and an output circuit for said detector.

6. A frequency converter unit comprising a radio-frequency ampliiier having a tuned plate circuit which consists of a concentric iine having an inner conductor and an outer conductor, an oscillator having a tuned output circuit which consists of a concentric line having an inner conductor and an outer conductor, said concentric lines being substantially parallel to each other, a compartment of conducting material bridging said outer conductors, a detector tube having an input circuit including input electrodes and having at least one input electrode terminal positioned inside said compartment, said detector tube being positioned with its longitudinal axis substantially perpendicular to the plane of said concentric lines, each or" said outer conducto-rs having openings therein looking into said compartment to couple said amplifier and said oscillator to said detector, a portion. of one of said outer conductors adjacent to the opening therein being common to said detector input circuit and to the tuned circuit in which said last conductor is included, and an output circuit for' said detector.

ALFRED l-I. TURr MR.

REFERENCES errno The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,200,023 Dallenbach May 7, 1940 2,277,638 George Mar. 2e, 1942 

